Conventionally, a powertrain of a vehicle includes a transmission which changes torque and/or the number of rotations of a driving apparatus including, for example, an engine and/or an electric motor, which is used for driving a driving wheel, so that the torque and/or rotations are transmitted to the driving wheel according to running conditions of the vehicle. There are some types of transmissions including, for example, a normally-meshed type transmission. For example, a known normally-meshed type transmission includes plural idler gears, each of which is fitted to, that is, provided at a rotary shaft connected to the driving wheel to be rotatable relative to the rotary shaft and not to be movable in a direction of a rotational axis, and plural gears, which are provided around a periphery of a counter shaft arranged to be parallel to the rotary shaft. The idler gears and the gears normally mesh with each other. According to the known normally-engaged type transmission, a sleeve is spline-fitted to the rotary shaft to be movable in the direction of the rotational axis, and the sleeve is arranged side by side with the idler gear. Engaging teeth (spline), which are provided at a joining surface of the sleeve which is joined to the idler gear, are brought to be engaged with engaged teeth (dog clutch teeth), which are provided at a joined surface of the idler gear. Thus, the idler gear engaged with the sleeve and the rotary shaft rotate integrally with each other. As the idler gear which rotates integrally with the rotary shaft and the gear of the counter shaft which meshes with the idler gear rotate in association with each other, torque and/or the number of rotations of the rotary shaft is transmitted to the counter shaft. A shifting operation is performed by selecting, from among the plural idler gears which include different numbers of teeth to each other, the idler gear that is to be rotated integrally with the rotary shaft and by bringing the sleeve into engagement with the selected idler gear. Depending on a timing at which the sleeve is pressed against the idler gear, there may be a case where the sleeve and the idler gear fail to engage with each other properly.
In such an instance where the sleeve is not properly engaged with the idler gear, according to JPH11-82710A (hereinafter referred to as Patent reference 1), torque with which the sleeve is pushed against the idler gear-side is once reduced, and after this, the sleeve is pushed against the idler-gear side again with a large torque in order to engage the sleeve and the idler gear with each other properly.
According to Patent reference 1, in a case where the sleeve is not brought into engagement with the idler gear, only an engagement operation is performed again. Therefore, without starting a shifting operation from the beginning, the sleeve and the idler gear are brought into engagement with each other.
According to the known shift control method described in Patent reference 1, however, a timer is used to determine that the sleeve is unable to be brought into engagement with a dog clutch of the idler gear. In a case where the sleeve does not reach a predetermined engagement position even though a predetermined time has passed, a reentry control, under which the sleeve is brought into engagement with the idler gear again, is executed. Thus, an entry control end time before the reentry, which is set by the timer, needs to be set at a value that is equal to or longer than a period of time for the sleeve to move to the predetermined position properly (that is, the period of time for the sleeve to engage with the dog clutch without being bounced back by the dog clutch). Accordingly, at a time point at which it is determined that the sleeve is unable to be brought into engagement with the dog clutch of the idler gear, the dog clutch is already pushed against the sleeve, and thus a difference in the number of rotations between the sleeve and the idler gear is already reduced to be minute or slight. Therefore, it takes time until the sleeve and the idler gear come to the next position at which the sleeve and the idler gear are engaged with each other. Alternatively, it takes longer time until the sleeve and the idler gear engage with each other next because the sleeve and the idler gear co-rotate with each other. As a result, a time for the shifting operation may be long.
A need thus exists for a dog clutch control apparatus for an automated transmission, which is not susceptible to the drawback mentioned above.